Floating dredge motion compensator

ABSTRACT

Apparatus automatically compensating for relative vertical movement between a dredging vessel and its cutter, or other formation removing mechanism, to maintain a predetermined vertical position of the cutter mechanism despite vertical motion of the floating dredge vessel caused by sea conditions. The compensating apparatus includes a cylinder and piston device containing a hydraulic fluid under pressure exerting a preselected lifting force on the cutter mechanism and automatically extensible and contractable to permit the vessel to move without effecting movement of the cutter mechanism and the force that such mechanism exerts on the formation.

Larralde Mar. 19, 1974 FLOATING DREDGE MOTION COMPENSATOR [75] Inventor:Edward Larralde, Santa Barbara,

' Calif.

[73] Assignee: Vetco Offshore Industries, Inc.,

Ventura, Calif.

[22] Filed: Aug. 24, 1972 211 Appl. No.z283,,473

52 us. c1. 37/67,37/72 [51] Int. Cl E02f 3/90 [58] Field of Search37/72, 67; 254/172 [56] References Cited v UNITED STATES PATENTS3.579.872 5/1971 Jantzen ..37/72x 318.859 5/1885 Bowers 3.512.28l 5/1970Hadjidakis ..37/72x FOREIGN PATENTS OR APPLICATIONS 851.333 /1960 GreatBritain 37 72 32 I "39 y ,l/

PI-1 l g1 A 14 F V C 13 Primary Examiner-R0bert E. Pulfrey AssistantExaminer-Clifford D. Crowder Attorney, Agent, or Firm-Bernard Krieg'el[5 7] ABSTRACT Apparatus automatically compensating for relativevertical movement between a dredging vessel and its cutter, or otherformation removing mechanism, to maintain a predetermined verticalposition of the cutter mechanism despite vertical motion of the floatingdredge vessel caused by sea conditions. The compensating apparatusincludes a cylinder and piston device containing a hydraulic fluid underpressure exerting a preselected lifting force on the cutter mechanismand automatically extensible and contractable to permit the vessel tomove without effecting movement of the cutter mechanism and the forcethat such mechanism exerts on the formation.

16 Claims, 3 Drawing Figures 1 FLOATING DREDGE MOTION COMPENSATOR Thepresent invention relates to dredges, and more particularly to motioncompensating apparatus for dredging vessels floating in a sea or otherbody of water, to isolate the cutter mechanisms of the dredges from thevertical or pitching motion of the floating vessels under seaconditions.

Floating dredging, vessels are subject to vertical motion caused bysea'conditions, such vertical motion seriously impairing the operationof the dredge in cutting the formation underlying the sea, ocean orother body of water, and also reducing the rate at which the spoil maybe removed. In addition, such vertical motion of the dredge vesselimposes severe loads on the dredge ladder and the hull structure of thevessel. Long swells from the open sea are common in harbor mouthdredging, while short swells resulting from ships passing generallyresult in a complex hull motion. Swells having length similar to orlonger than the dredge hull cause pitching of the hull, and, therefore,great variations in the force with which thecutter head bears againstthe formation.

By virtue of the present invention, a compensator apparatus is providedwhich is capable of isolating the vessel movement from its cuttermechanism, whereby the desired weight or drilling force is maintained onthe cutter head irrespective of heaving of the vessel in a sea, ocean orother body of water.

In general, a compensator apparatus includes a cylinder and pistondevice connected between a dredge ladder and the supporting structure ofthe dredge, which is carried by the vessel hull. The ladder is pivotallymounted on the hull, carrying the drive mechanism and the cutter, whichis to operate upon the formation underlying the body of water. Theposition of the ladder and the cutter mechanism carried thereby isdetermined by a cable support, which can be used to raise or lower thecutter relative to the hull. In apparatus embodying the presentinvention, the ladder and the cutter mechanism are supportedhydraulically or fluidly by interposing a compensating apparatus betweenthe travelling sheaves of the cable support and the free end of theladder. The apparatus relies upon the maintenance of a required pressureina fluid, such as a hydraulic fluid disposed within a cylinder andpiston device of the apparatus, such pressure being maintained in theabsence or presence of longitudinal movement of the cylinder and pistonportion of the device with respect to each other, the hydraulic fluidexerting a continuous, substantially constant stress on the ladder. Inother words, the hydraulic fluid supports a portion of the weight of theladder and the cutter mechanism, the remainder of its weight beingexerted on the cutter and against the formation being removed, suchremainder of the drilling or cutter weight being maintainedsubstantially constant since the relative longitudinal movement betweenthe cylinder and piston, within the limits of their longitudinal travelwith respect to each other, has no effect on the supporting force of thehydraulic fluid under pressure within the cylinder. Despite heaving orother vertical-movement of the hull portion of the dredge, the free endof the ladder and the cutter carried thereby will not movecorrespondingly to any appreciable degree, the movement of the dredgingvessel or hull being incapable of transmission to the ladder and itscutter, which will remain in a predetermined position with respect tothe formation being drilled.

It is, accordingly, apparent that the extensible hydraulic or fluidcompensator maintains a generally constant suspension force on theladder, causing the cutter to bear against the formation with thedesired force, despite pitching or heaving of the dredge or its othervertical movement.

Another object of the invention is to provide an apparatus in which thecable system used for elevating the ladder and cutter mechanism carriedthereby can function to raise or lower the cutter portion of theapparatus, including its ladder structure, to and from an operativeposition with respect to the formation without the necessity for suchelevating force being transmitted through the fluid, such as hydraulicfluid, in the cylinder and piston compensator. In a more limited sense,

this aspect of the invention is achieved by providing a lock mechansimthat secures the cylinder and piston together when the cylinder andpiston are fully telescoped one with the other, such lock mechanismpreferably being selectively operated from a remote location. Thus, thehydraulic fluid need not even be under pressure once the lock has beenmade effective, since the entire lifting force will be transmittedbetween the cylinder and piston portions of the compensator to the lockmechanism, and without the necessity for any of such force beingtransmitted through the hydraulic fluid within the cylinder. By virtueof providing a lock, such as a mechanical lock, between the cylinder andpiston portions of the apparatus, the hydraulic fluid within thecylinder need not have an unduly high unit pressure imposed upon it.This is due to the fact that the load imposed upon the cable supportmechanism in raising the ladder and the cutter mechanism out of thewater is considerably greater than the hydraulic force required tosupport only a portion of the load or weight of the ladder and thecutter mechanism during the performance of a drilling operation, inwhich the hydraulic fluid maintains the ladder and the cutter mechanismin a predetermined position without any substantial adverse affect bythe pitching or heaving of the vessel in the water.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of a formin which it may be embodied. This formis shown in the drawingsaccompanying and forming part of the present specification. It will nowbe described in detail, for the purpose of illustrating the generalprinciples of the invention; but it is to be understood that suchdetailed description is not to be taken in a limiting sense.

Referring to the drawings:

FIG. 1 is a side elevational view, shown somewhat diagrammatically, of adredge floating in a body of water for drilling a formation underlying abody of water;

FIG. 2 is an enlarged plan view, parts being shown in section, of thecylinder and piston portions of the apparatus in a fully collapsedposition and locked to one another;

FIG. 3 is an elevational view, taken at right angles to the viewillustrated in FIG. 2, disclosing the cylinder and piston portions ofthe apparatus in their unlocked or operative condition.

As disclosed in FIG. 1, a dredging vessel V is provided having a buoyanthull H floating in a sea, ocean or other body of water S, and adapted tocut into the formation F underlying the body of water throughappropriate rotation and manipulation of a cutter head C brought to bearagainst the formation. A ladder structure L carries the cutter mechanismM, this ladder structure having its rear portion suitably pivotallysupported by the buoyant hull H, such as by one or a plurality of pivotpins 10, the ladder structure being of a suitable length and extendingforwardly of the hull a suitable distance from the pivot support 10,which, for example, may be about 200 feet, the ladder structure L andthe cutter mechanism M carried thereby representing a total weight ofperhaps 200,000 to 300,000 pounds.

The rear portion of the ladder structure carries a suitable drive motor11 adapted to rotate a drive shaft 12 extending through a bearingsupport 13 secured to the forward end of the ladder structure, andfurther passing through a bearing support 14 behind the forward bearingsupport. The cutter head C is attached to the drive shaft 12 for bearingagainst and cutting the formation F. Such cutter head may be ratherlarge, for example, weighing about 40,000 pounds. The weight of theladder structure L not supported by the buoyant hull H is supported inpart by the cutter head C bearing against the formation F, which effectsthe cutting action as a result of such weight, as well as by forward andlateral movements of the cutter head through use of suitable knownmechanisms (not shown), and which per se form no part of the presentinvention. The weight of the ladder structure and the cutter mechanism Mcarried thereby, which is not to be imposed upon the cutter head C, issupported through a compensator apparatus A and a cable mechanism Battached thereto.

The compensator apparatus also permits relative vertical movement of thefloating vessel V and the structures carried thereby with respect to thecutter head C, and without substantially modifying the weight imposed onthe cutter head, or its position against the formation F. As disclosed,a suitable frame 15, such as an A frame, has its lower end pivotallymounted on the hull H by means of a pivot pin 16, its upper endrotatably supporting one or a plurality of upper sheaves 17, the A framebeing suitably supported in an upwardly and forwardly inclined positionthrough an intervening tension line or cable 18 extending between theupper end of the frame and the forward portion of a fixed framestructure 19 secured to the buoyant hull H. The upper portion of thecompensating apparatus A is connected by a pivot pin 20 to one or morelinks 21, the upper part of which carries one or a plurality ofrotatable sheaves 22 movable toward and away from the upper portion ofthe A frame 15. A suitable cable system 23 extends around the upper andlower sheaves 17, 22, and around a pulley 24 rotatably mounted on theforward portion of the frame 19, the cable being wound upon the drums 25of a suitable winch 26 which is manipulatable in a known manner to pullthe travelling sheaves 22 towards the upper sheaves 17, or allow thetravelling sheaves to move downwardly from the upper sheaves. Throughappropriate manipulation of the winch, the ladder structure L and cuttermechanism M carried thereby can be swung about the pivot support 10, thetension in the cables 23 being transmitted through the compensatorapparatus A to the forward portion of the ladder bearing support 14. Asdescribed hereinbelow, the ladder structure L and the cutter mechanism Mcan be elevated completely from the water, or they can be lowered to adesired position below the surface of the water.

The compensator apparatus includes an elongate cylinder structure 30,the upper end of which is pivotally connected through the pivot 20 tothe lower portion of the links 21. The cylinder structure includes anupper cylinder portion 31 whose lower cylinder head 32 is suitablysecured to a connector 33 having upper pivot pins or trunnions 34extending laterally therefrom, on which are pivotally mounted links 35extending downwardly to a lower guide 36, the lower ends of the linksbeing pivotally mounted on pins 37 suitably affixed to the upper portionof the guide. Movable longitudinally within the cylinder structure 30 isa piston structure 38 including a piston 39 slidable along the innerwall of the cylinder 31 and having a piston rod 40 attached thereto andextending slidably through the lower cylinder head 32 to a positionbelow the connector 33. The piston rod structure 38 further includes alower portion 41 pivotally secured to the upper rod portion 40 by aclevis 42 attached to the lower end of the upper rod portion and a pin43 passing through the arms 44 of the clevis and through the upper end45 of the lower portion 41 straddled by the clevis arms. The lower rodportion 41 is slidable longitudinally through the lower guide 36,extending downwardly a sufficient distance for pivotal attachment to thebearing support 14.

When the piston rod structure 38 is in its uppermost position within andrelative to the cylinder 31, as determined by the abutting of a stop orlimit sleeve 50 suitably welded or otherwise affixed to the lower rodstructure 41 with the lower end of the guide 36 (FIG. 2), the piston rodstructure and cylinder structure 30' can be mechanically secured to oneanother to prevent their relative movement. With the piston rodstructure in its uppermost position with respect to the cylinderstructure, a suitable lock pin 51 can be inserted through opposed holesor bores 52 in the guide 36 and through a central hole 53 in the lowerrod structure aligned therewith. This pin 51 is inserted hydraulicallyinto the locked position illustrated in FIG. 2, or removed therefrom,from a remote point on board the dredging vessel. As specificallyillustrated, a lock cylinder 54 is suitably secured, as by screws 55, tothe exterior of the guide 36, this cylinder containing a piston 56secured to the lock pin 51. The introduction of suitable fluid underpressure through a suitable line 57 into the rod end of the cylinder 54will cause the piston 56 to move longitudinally toward the head end ofthe cylinder to fully withdraw the lock pin from the rod structure,thereby permitting relative longitudinal movement to occur between thepiston rod structure 38 and cylinder structure 30. On the other hand,the bleeding of the fluid under pressure from the rod end of thecylinder and its introduction through a suitable line 58 into the headend of the structure will shift the piston 56 in a direction away fromthe head end of the cylinder and insert the lock pin 51 through thealigned holes 52, 53 in the guide 36 and lower rod 41, thereby lockingthe parts 38, 40 together.

The upper and lower piston rod portions 40, 41 of the apparatus arearticulated with respect to one another through their pininterconnection 43 to avoid bending and binding in the parts because ofthe very substantial weight imposed upon them by the ladder structure Land the cutter mechanism M carried thereby. The inclination of thecompensating apparatus A relative to the ladder structure L introduces abending moment into the compensator structure, which would tend to bindthe upper piston rod structure 40 within the cylinder 31 and introduceundue friction resisting relative movement between the cylinder 31 andthe piston 39 and rod 40, as well as effect leakage of the seals 60 inthe system between the head 32 and rod 40. The articulated relationbetween the upper and lower piston rod structures 40, 41 prevents orminimizes such binding. The angle Y between the upper and lower pistonrod structures has been exaggerated in FIG. 3 of the drawings. Actually,the included angle is about 83 to 85, the misalignment between the upperand lower rod structures being only a matter of about 5 to 7.

The compensator cylinder 31 contains a liquid 70 under pressure derivedfrom a suitable accumulator 71 mounted on the drilling vessel, theliquid passing through a suitable hose 72, controlled by a valve 73, andinto the head end 32 of the cylinder below the piston 39. The pressureof the liquid is maintained by a suitable compressed gas 74, such ascompressed air, in the upper portion of the accumulator 7,1, thepressure of the gas being transferred through a suitable floatingaccumulator piston 75 to the liquid 70. The compressor piston 39 ismovable longitudinally relatively within the cylinder 31, the liquidpressure therein being maintained at all times since the liquid 70 canpass through the hose 72 into and from the accumulator 71. The hydraulicand compressed airsystem for maintaining the liquid in the cylinderunder pressure per se forms no part of the present invention. Adescription of such system is set forth in the application of EdwardLarralde, Ser. No. 222,919, filed Feb. 2, 1972, for Variable RateHydraulic-Pneumatic Weight.Control and Compensating Apparatus, to whichattention is directed.

In the operation of the apparatus illustrated in the drawings, thepressure of the compressed gas or air 74 is selected which will conformto the desired unit pressure of the liquid 70 acting within thecompensator cylinder 30, such liquid pressure depending upon theformation being cut by the cutter head C, the pressure relieving thecutter head of a required portion of the weight of the ladder structureL and the cutter mecha-v nism M mounted thereon. The vertical positionof the cutter head is controlled by the winch 26, which will either feedoff cable 23 or pull in cable to raise or lower the ladder L and thecutter head C supported thereby. Actually, it is not necessary tocontinually manipulate the winch to determine the vertical position ofthe cut ter head Csince the position 39 can lower in the cylinder 30 asthe cutter head drills in a downward direction, the cuttings beingsuitablyremoved from the location of the head C in any suitable manner,as through use of suction equipment, which forms no part of the presentinvention and which is therefore neither illustrated nor describedherein. The pressure of the liquid 70 in the cylinder remainssubstantially constant and will determine the net weight of the ladderstructure L and cutter mechanism M imposed on the cutter head C.Pitching or heaving of the vessel in the water, as, for example, as aresult of swells, will not modify the position of the cutter head or thenet drilling weight imposed thereon, since elevation of the hull H andof the compensator cylinder structure 30 can readily occur with respectto the piston structure 38, such extensible movement of the cylinderstructure relative to the piston structure merely resulting in theliquid 70 flowing through the hose 72 toward the accumulator 71, butwithout modifying the pressure of the liquid acting in an upwarddirection in the piston 39, the tensile force imposed by the liquid onthe piston structure remaining unchanged. On the other hand, lowering ofthe hull H will result in a corresponding relative descent of thecylinder structure 30 along the piston structure 38, the liquid movingfrom the accumulator 71 through the hose 72 back into the cylinder 31without the unit pressure of the liquid being modified, such liquidunder pressure still maintaining the same degree of tension in thepiston rod structure 38, resulting in the forward portion of the ladderand the cutter head C remaining in position and without partaking of anydegree of vertical movement that would substantially modify the drillingweight of the cutter head C against the formation F and of thecontinuous drilling effectiveness of the head in the formation beingremoved.

It is, accordingly, apparent that the liquid pressure in the compensatorremains substantially constant, the compensator being capable ofextending or contracting in accordance with vertical movement of thevessel in the water without essentially modifying the position of thecutter head C or of its drilling weight or force against the formation Fbeing cut.

In the event it is desired to elevate the ladder structure L and thecutter mechanism M from the water, the winch 26 is appropriatelymanipulated to cause the travelling sheaves 22 to lower with respect tothe upper sheaves 17, until the cylinder structure 30 moves downwardlyto its fullest extent along the piston structure 38 and the guide 36abuts the limit sleeve 50 affixed to the lower piston rod member 41,thereby aligning the holes or bores 53, 52 in the rod member 41 and theguide 36. Fluid pressure can then be directed into the cylinder 54through the head end fluid-line 58 to move the piston toward the rod 41and shift the lock pin 51 through the aligned holes 52, 53, therebylocking the cylinder structure 30 and piston structure 38 to oneanother. The winch 26 can then be manipulated to move the travellingsheaves 22 toward the upper sheaves 17 and elevate the ladder Lcompletely from the water S, the hydraulic fluid in the cylinder 31 notbeing required to transmit any of the load being lifted. Accordingly,when the comparator system A is to be made functional, only that liquidpressure is required in the cylinder 31 for relieving part of the weightof the ladder L and cutter mechanism M fromthe cutter head C. A unitliquid pressure for supporting the entire load of the ladder L andcutter mechanism M is not required.

In the event it is desired to vary the lifting force on the pistonstructure 38 and, therefore, the resultant load imposed on the cutterhead C, it is only necessary to change the unit pressure of thecompressed air 74, or other gas, in the accumulator 71, which willcorrespondingly change the unit pressure of the liquid 70 in the system,as set forth in the above-identified patent application, Ser. No.222,919. Usually, if soft formations are being cut, the unit pressurewill be greater in order that the cutter head be relieved of a greaterportion of the weight of the ladder L and of the cutter mechanism M. Indrilling hard formations, the unit pressure will be decreased to cause acorresponding greater load to be imposed on the cutter head C. Theresultant load on the cutter head will remain substantially constantdespite extensive pitch or heave of the dredge in the water, asdescribed above.

I claim:

1. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said mechanism; means extending forwardly ofsaid vessel and supporting one of said means from said vessel; meansoperatively connecting said other of said means to said cuttermechanism; means for maintaining a fluid medium under pressure in saidcylinder means on one side of said piston means as said piston means andcylinder means move longitudinally with respect to each other to providean upwardly directed force on said cutter mechanism supporting at leasta portion of the weight of said cutter mechanism and thereby retainingthe drilling weight of said cutter device against the formation at aselected value; and means for maintaining said fluid medium in saidcylinder means at a substantially constant selected pressure.

2. In dredging apparatus as defined in claim 1; said one of said meansbeing said cylinder means; said other of said means being said pistonmeans.

3. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said mechanism; means supporting one of saidmeans from said vessel; means operatively connecting said other of saidmeans to said cutter mechanism; means for maintaining a fluid mediumunder pressure in said cylinder means on one side of said piston meansas said piston means and cylinder means move longitudinally with respectto each other to provide an upwardly directed force on said cuttermechanism supporting at least a portion of the weight of said cuttermechanism and thereby retaining the drilling weight of said cutterdevice against the formation at a selected value; and means formaintaining said fluid medium in said cylinder means at a substantiallyconstant selected pressure; said supporting means including means forraising and lowering said one of said means with respect to said vessel,said supporting means extending above and connected to the upper portionof said one of said means.

4. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said mechanism; means supporting one of saidmeans from said vessel; means operatively connecting said other of saidmeans to said cutter mechanism; means for maintaining a fluid mediumunder pressure in said cylinder means on one side of said piston meansas said piston means and cylinder means move longitudinally with respectto each other to provide an upwardly directed force on said cuttermechanism supporting at least a portion of the weight of said cuttermechanism and thereby retaining the drilling weight of saidcutter deviceagainst the formation at a selected value; and means for maintainingsaid fluid medium in said cylinder means at a substantially constantselected pressure; said one of said means being said cylinder means;said other of said means being said piston means; said supporting meansincluding means for raising and lowering said cylinder means withrespect to said vessel; said supporting means extending above andconnected to the upper portion of said cylinder means.

5. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; means supporting one ofsaid means from said vessel; means operatively connecting said other ofsaid means to said cutter mechanism; means for maintaining a fluidmedium under pressure in said cylinder means on one side of said pistonmeans as said piston means and cylinder means move longitudinally withrespect to each other to provide an upwardly directed force on saidcutter mechanism supporting at least a portion of the weight of saidcutter mechanism and thereby retaining the drilling weight of saidcutter device against the formation at a selected value; said supportingmeans including means for raising and lowering said one of said meanswith respect to said vessel; and releasable lock means for securing saidcylinder means and piston means to each other whereby raising andlowering of said one of said means raises and lowers said cuttermechanism with respect to said vessel.

6. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; means supporting one ofsaid means from said vessel; means operatively connecting said other ofsaid means to said cutter mechanism; means for maintaining a fluidmedium under pressure in said cylinder means on one side of said pistonmeans as said piston means and cylinder means move longitudinally withrespect to each other to provide an upwardly directed force on saidcutter mechanism supporting at least a portion of the weight of saidcutter mechanism and thereby retaining the drilling weight of saidcutter device against the formation at a selected value; said one ofsaid means being said cylinder means; said other of said means beingsaid piston means; said supporting means including means for raising andlowering said cylinder means with respect to said vessel; and releasablelock means for securing said cylinder means and piston means to eachother whereby raising and lowering of said cylinder means raises andlowers said cutter mechanism with respect to said vessel.

7. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said mechanism; means supporting one of saidmeans from said vessel; means operatively connecting said other of saidmeans to said cutter mechanism; means for maintaining a fluid mediumunder pressure in said cylinder means on one side of said piston meansas said piston means and cylinder means move longitudinally with respectto each other to provide an upwardly directed force on said cuttermechanism supporting at least a portion of the weight of said cuttermechanism and thereby retaining the drilling weight of said cutterdevice against the formation at a selected value; and means formaintaining said fluid medium in said cylinder means at a substantiallyconstant selected pressure; said supporting means extending above andconnected to the upper portion of said one of said means; saidsupporting means including one or more lower sheaves connected to saidone of said means, one or more upper sheaves carried by said vessel, awinch, and cable means passing over said upper and lower sheaves andconnected to said winch to be moved thereby for raising and loweringsaid one of said means with respect to said vessel.

8. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said mechanism; means supporting one of saidmeans from said vessel; means operatively connecting said other of saidmeans to said cutter mechanism; means for maintaining a fluid mediumunder pressure insaid cylinder means on one side of said piston means assaid piston means and cylinder means move longitudinally with respect toeach other to provide an upwardly directed force on said cuttermechanism supporting at least a portion of the weight of said cuttermechanism and thereby retaining the drilling weight of said cutterdevice against the formation at a selected value; and means formaintaining said fluid medium in said cylinder means at a substantiallyconstant selected pressure; said supporting means extending above andconnected to the upper portion of said cylinder means; said supportingmeans including one or more lower sheaves connected to said cylindermeans, one or more upper sheaves carried by said vessel, a winch, andcable means passing over said upper and lower sheaves and connected tosaid winch to be moved therebyfor raising and lowering said cylindermeans with respect to said vessel.

9. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; means supporting one ofsaid means from said vessel; means operatively connecting said other ofsaid means to said cutter mechanism; means for maintaining a fluidmedium under pressure in said cylinder means on one side of said pistonmeans as said piston means and cylinder means move longitudinally withrespect to to said one of said means, one or more upper sheaves carriedby said vessel, a winch, and cable means passing over said upper andlower sheaves and connected to said winch to be moved thereby forraising and lowering said one'of said means with respect to said vessel;and releasable lock means for securing said cylinder means and pistonmeans to each other whereby raising and lowering of said one of saidmeans raises and lowers said cutter mechanism with respect to saidvessel.

It). In dredging apparatus: a vessel floating in a body of water; acutter mechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; means supporting one ofsaid means from said vessel; means operatively connecting said other ofsaid means to said cutter mechanism; means for maintaining a fluidmedium under pressure in said cylinder means on one side of said pistonmeans as said piston means and cylinder means move longitudinally withrespect to each other to provide an upwardly directed force on saidcutter mechanism supporting at least a portion of the weight of saidcutter mechanism and thereby retaining the drilling weight of saidcutter device against the formation at a selected value; said supportingmeans including one or more lower sheaves connected to said cylindermeans, one or more upper sheaves carried by said vessel, a winch, andcable means passing over said upper and lower sheaves and connected tosaid winch to be moved thereby for raising and lowering said cylindermeans with respect to said vessel; and releasable lock means forsecuring said cylinder means and piston means to each other wherebyraising and lowering of said cylinder means raises and lowers saidcutter mechanism with respect to said vessel.

1 1; In dredging apparatus: a vessel floating in a body of water; aladder pivotally connected to said vessel and extending therefrom; acutter mechanism carried by said ladder and including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said ladder; means extending forwardly ofsaid vessel and supporting said cylinder means from said vessel; meansoperatively connecting said piston means to said ladder; and means formaintaining a fluid medium under pressure in said cylinder means on oneside of said piston means as said piston means and cylinder means movelongitudinally with respect to each other to provide an upwardlydirected force on said ladder and cutter mechanism to support at least aportion of the weight of said ladder and cutter mechanism and therebyretain the drilling weight of said cutter device against the formationat a selected value; and means for maintaining said fluid medium in saidcylinder means at a substantially constant selected pressure.

12. In dredging apparatus: a vessel floating in a body of water; aladder pivotally connected to said vessel and extending therefrom; acutter mechanism carried by said ladder and including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said ladder; means supporting said cylindermeans from said vessel; means operatively connecting said piston meansto said ladder; and means for maintaining a fluid medium under pressurein said cylinder means on one side of said piston means as said pistonmeans and cylinder means move longitudinally with respect to each otherto provide an upwardly directed force on said ladder and cuttermechanism to support at least a portion of the weight of said ladder andcutter mechanism and thereby retain the drilling weight of said cutterdevice against the formation at a selected value; and means formaintaining said fluid medium in said cylinder means at a substantiallyconstant selected pressure; said supporting means including means forraising and lowering said cylinder means with respect to said vessel;said supporting means extending above and connected to the upper portionof said cylinder means.

13. In dredging apparatus: a vessel floating in a body of water; aladder pivotally connected to said vessel and extending therefrom; acutter mechanism carried by said ladder and including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; means supporting saidcylinder means from said vessel; means operatively connecting saidpiston means to said ladder; means for maintaining a fluid medium underpressure in said cylinder means on one side of said piston means as saidpiston means and cylinder means move laterally with respect to eachother to provide an upwardly directed force on said ladder and cuttermechanism to support at least a portion of the weight of said ladder andcutter mechanism and thereby retain the drilling weight of said cutterdevice against the formation at a selected value; said supporting meansincluding means for raising and lowering said cylinder means withrespect to said vessel; and releasable lock means for securing saidcylinder means and piston means to each other whereby raising andlowering of said cylinder means raises and lowers said ladder and cuttermechanism with respect to said vessel.

14. In dredging apparatus as defined in claim 13; said cylinder meansincluding a guide; said piston means including a piston in said cylindermeans, an upper piston rod portion secured to said piston and extendingfrom said cylinder means, a lower piston rod portion pivotally connectedto said upper rod portion and slidable in said guide; said lower rodportion being connected to said ladder; said releasable lock meanssecuring said guide to said lower rod portion whereby raising andlowering of said cylinder means raises and lowers said ladder and cuttermechanism.

15. In dredging apparatus: a vessel floating in a body of water; aladder pivotally connected to said vessel and extending therefrom; acutter mechanism carried by said ladder and including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; means supporting saidcylinder means from said vessel; means operatively connecting saidpiston means to said ladder; means for maintaining a fluid medium underpressure in saidv cylinder means on one side of said piston means assaid piston means and cylinder means move laterally with respect to eachother to provide an upwardly directed force on said ladder and cuttermechanism to support at least a portion of the weight of said ladder andcutter mechanism and thereby retain the drilling weight of said cutterdevice against the formation at a selected value; said cylinder meansincluding a guide; said piston means including a piston in said cylindermeans; an upper piston rod portion secured to said piston and extendingfrom said cylinder means, a lower piston rod portion pivotally connectedto said upper rod portion and slidable in said guide; said lower rodportion being connected to said ladder.

16. In dredging apparatus: a vessel floating in a body of water; aladder pivotally connected to said vessel and extending therefrom; acutter mechanism carried by said ladder and including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; means supporting saidcylinder means from said vessel; means operatively connecting saidpiston means to said ladder; means for maintaining a fluid medium underpressure in said cylinder means on one side of said piston means as saidpiston means and cylinder means move laterally with respect to eachother to provide an upwardly directed force on said ladder and cuttermechanism to support at least a portion of the weight of said ladder andcutter mechanism and thereby retain the drilling weight of said cutterdevice against the formation at a selected value; said supporting meansincluding one or more lower sheaves connected to said cylinder means,one or more upper sheaves carried by said vessel, a winch, and cablemeans passing over said upper and lower sheaves and connected to saidwinch to be moved thereby for raising and lowering said cylinladder andcutter mechanism.

29 3 32 "um rmo s'm'mss' iuxrmazwr 01mm;

CEREIFICZHE G1 CORRECTIUN 3,797,139 Dated March 19 9 1g Ed v ard Larralde v Patent No.

Iuvuntorh'.)

u certified that error zrppcnrs in the abovw-idcntifivd patent 'r' I J-and that said Letters Patent are heuquby corrected as shown below:

Column '2, line 21f canc l "wifih" and substitute -with1n--. Column. 5,line 24:" cancel oompress'oxg" and substitute I i I I -comp'enstor---.

Signediand ise aled this 1st day of Octobe'r l974'.

(SEAL) Attest: s McCOY M. oussoN JR. c. MARSHALL DANN Attesting OfficerCommissioner of Patents

1. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said mechanism; means extending forwardly ofsaid vessel and supporting one of said means from said vessel; meansoperatively connecting said other of said means to said cuttermechanism; means for maintaining a fluid medium under pressure in saidcylinder means on one side of said piston means as said piston means andcylinder means move longitudinally with respect to each other to providean upwardly directed force on said cutter mechanism supporting at leasta portion of the weight of said cutter mechanism and thereby retainingthe drilling weight of said cutter device against the formation at aselected value; and means for maintaining said fluid medium in saidcylinder means at a substantially constant selected pressure.
 2. Indredging apparatus as defined in claim 1; said one of said means beingsaid cylinder means; said other of said means being said piston means.3. In dredging apparatus: a vessel floating in a body of water; a cuttermechanism carried by and extending forwardly from said vessel andmovable with respect thereto, said mechanism including a cutter devicefor cutting a formation submerged In the body of water; cylinder means;piston means slidable in said cylinder means; both of said means beinglocated above and overlying said mechanism; means supporting one of saidmeans from said vessel; means operatively connecting said other of saidmeans to said cutter mechanism; means for maintaining a fluid mediumunder pressure in said cylinder means on one side of said piston meansas said piston means and cylinder means move longitudinally with respectto each other to provide an upwardly directed force on said cuttermechanism supporting at least a portion of the weight of said cuttermechanism and thereby retaining the drilling weight of said cutterdevice against the formation at a selected value; and means formaintaining said fluid medium in said cylinder means at a substantiallyconstant selected pressure; said supporting means including means forraising and lowering said one of said means with respect to said vessel,said supporting means extending above and connected to the upper portionof said one of said means.
 4. In dredging apparatus: a vessel floatingin a body of water; a cutter mechanism carried by and extendingforwardly from said vessel and movable with respect thereto, saidmechanism including a cutter device for cutting a formation submerged inthe body of water; cylinder means; piston means slidable in saidcylinder means; both of said means being located above and overlyingsaid mechanism; means supporting one of said means from said vessel;means operatively connecting said other of said means to said cuttermechanism; means for maintaining a fluid medium under pressure in saidcylinder means on one side of said piston means as said piston means andcylinder means move longitudinally with respect to each other to providean upwardly directed force on said cutter mechanism supporting at leasta portion of the weight of said cutter mechanism and thereby retainingthe drilling weight of said cutter device against the formation at aselected value; and means for maintaining said fluid medium in saidcylinder means at a substantially constant selected pressure; said oneof said means being said cylinder means; said other of said means beingsaid piston means; said supporting means including means for raising andlowering said cylinder means with respect to said vessel; saidsupporting means extending above and connected to the upper portion ofsaid cylinder means.
 5. In dredging apparatus: a vessel floating in abody of water; a cutter mechanism carried by and extending forwardlyfrom said vessel and movable with respect thereto, said mechanismincluding a cutter device for cutting a formation submerged in the bodyof water; cylinder means; piston means slidable in said cylinder means;means supporting one of said means from said vessel; means operativelyconnecting said other of said means to said cutter mechanism; means formaintaining a fluid medium under pressure in said cylinder means on oneside of said piston means as said piston means and cylinder means movelongitudinally with respect to each other to provide an upwardlydirected force on said cutter mechanism supporting at least a portion ofthe weight of said cutter mechanism and thereby retaining the drillingweight of said cutter device against the formation at a selected value;said supporting means including means for raising and lowering said oneof said means with respect to said vessel; and releasable lock means forsecuring said cylinder means and piston means to each other wherebyraising and lowering of said one of said means raises and lowers saidcutter mechanism with respect to said vessel.
 6. In dredging apparatus:a vessel floating in a body of water; a cutter mechanism carried by andextending forwardly from said vessel and movable with respect thereto,said mechanism including a cutter device for cutting a formationsubmerged in the body of water; cylinder means; piston means slidable insaid cylinder means; means supporting one of said means from saidvessel; means operatively connecting said other of said means to saidcutter mechanism; means for maintaining a fluid medium under pressure insaid cylinder means on one side of said piston means as said pistonmeans and cylinder means move longitudinally with respect to each otherto provide an upwardly directed force on said cutter mechanismsupporting at least a portion of the weight of said cutter mechanism andthereby retaining the drilling weight of said cutter device against theformation at a selected value; said one of said means being saidcylinder means; said other of said means being said piston means; saidsupporting means including means for raising and lowering said cylindermeans with respect to said vessel; and releasable lock means forsecuring said cylinder means and piston means to each other wherebyraising and lowering of said cylinder means raises and lowers saidcutter mechanism with respect to said vessel.
 7. In dredging apparatus:a vessel floating in a body of water; a cutter mechanism carried by andextending forwardly from said vessel and movable with respect thereto,said mechanism including a cutter device for cutting a formationsubmerged in the body of water; cylinder means; piston means slidable insaid cylinder means; both of said means being located above andoverlying said mechanism; means supporting one of said means from saidvessel; means operatively connecting said other of said means to saidcutter mechanism; means for maintaining a fluid medium under pressure insaid cylinder means on one side of said piston means as said pistonmeans and cylinder means move longitudinally with respect to each otherto provide an upwardly directed force on said cutter mechanismsupporting at least a portion of the weight of said cutter mechanism andthereby retaining the drilling weight of said cutter device against theformation at a selected value; and means for maintaining said fluidmedium in said cylinder means at a substantially constant selectedpressure; said supporting means extending above and connected to theupper portion of said one of said means; said supporting means includingone or more lower sheaves connected to said one of said means, one ormore upper sheaves carried by said vessel, a winch, and cable meanspassing over said upper and lower sheaves and connected to said winch tobe moved thereby for raising and lowering said one of said means withrespect to said vessel.
 8. In dredging apparatus: a vessel floating in abody of water; a cutter mechanism carried by and extending forwardlyfrom said vessel and movable with respect thereto, said mechanismincluding a cutter device for cutting a formation submerged in the bodyof water; cylinder means; piston means slidable in said cylinder means;both of said means being located above and overlying said mechanism;means supporting one of said means from said vessel; means operativelyconnecting said other of said means to said cutter mechanism; means formaintaining a fluid medium under pressure in said cylinder means on oneside of said piston means as said piston means and cylinder means movelongitudinally with respect to each other to provide an upwardlydirected force on said cutter mechanism supporting at least a portion ofthe weight of said cutter mechanism and thereby retaining the drillingweight of said cutter device against the formation at a selected value;and means for maintaining said fluid medium in said cylinder means at asubstantially constant selected pressure; said supporting meansextending above and connected to the upper portion of said cylindermeans; said supporting means including one or more lower sheavesconnected to said cylinder means, one or more upper sheaves carried bysaid vessel, a winch, and cable means passing over said upper and lowersheaves and connected to said winch to be moved thereby for raising andlowering said cylinder means with respect to said vessel.
 9. In dredgingapparatus: a vessel floating in a body of water; a cutter mechanisMcarried by and extending forwardly from said vessel and movable withrespect thereto, said mechanism including a cutter device for cutting aformation submerged in the body of water; cylinder means; piston meansslidable in said cylinder means; means supporting one of said means fromsaid vessel; means operatively connecting said other of said means tosaid cutter mechanism; means for maintaining a fluid medium underpressure in said cylinder means on one side of said piston means as saidpiston means and cylinder means move longitudinally with respect to eachother to provide an upwardly directed force on said cutter mechanismsupporting at least a portion of the weight of said cutter mechanism andthereby retaining the drilling weight of said cutter device against theformation at a selected value; said supporting means including one ormore lower sheaves connected to said one of said means, one or moreupper sheaves carried by said vessel, a winch, and cable means passingover said upper and lower sheaves and connected to said winch to bemoved thereby for raising and lowering said one of said means withrespect to said vessel; and releasable lock means for securing saidcylinder means and piston means to each other whereby raising andlowering of said one of said means raises and lowers said cuttermechanism with respect to said vessel.
 10. In dredging apparatus: avessel floating in a body of water; a cutter mechanism carried by andextending forwardly from said vessel and movable with respect thereto,said mechanism including a cutter device for cutting a formationsubmerged in the body of water; cylinder means; piston means slidable insaid cylinder means; means supporting one of said means from saidvessel; means operatively connecting said other of said means to saidcutter mechanism; means for maintaining a fluid medium under pressure insaid cylinder means on one side of said piston means as said pistonmeans and cylinder means move longitudinally with respect to each otherto provide an upwardly directed force on said cutter mechanismsupporting at least a portion of the weight of said cutter mechanism andthereby retaining the drilling weight of said cutter device against theformation at a selected value; said supporting means including one ormore lower sheaves connected to said cylinder means, one or more uppersheaves carried by said vessel, a winch, and cable means passing oversaid upper and lower sheaves and connected to said winch to be movedthereby for raising and lowering said cylinder means with respect tosaid vessel; and releasable lock means for securing said cylinder meansand piston means to each other whereby raising and lowering of saidcylinder means raises and lowers said cutter mechanism with respect tosaid vessel.
 11. In dredging apparatus: a vessel floating in a body ofwater; a ladder pivotally connected to said vessel and extendingtherefrom; a cutter mechanism carried by said ladder and including acutter device for cutting a formation submerged in the body of water;cylinder means; piston means slidable in said cylinder means; both ofsaid means being located above and overlying said ladder; meansextending forwardly of said vessel and supporting said cylinder meansfrom said vessel; means operatively connecting said piston means to saidladder; and means for maintaining a fluid medium under pressure in saidcylinder means on one side of said piston means as said piston means andcylinder means move longitudinally with respect to each other to providean upwardly directed force on said ladder and cutter mechanism tosupport at least a portion of the weight of said ladder and cuttermechanism and thereby retain the drilling weight of said cutter deviceagainst the formation at a selected value; and means for maintainingsaid fluid medium in said cylinder means at a substantially constantselected pressure.
 12. In dredging apparatus: a vessel floating in abody of water; a ladder pivotally connected to said vessel and extendIngtherefrom; a cutter mechanism carried by said ladder and including acutter device for cutting a formation submerged in the body of water;cylinder means; piston means slidable in said cylinder means; both ofsaid means being located above and overlying said ladder; meanssupporting said cylinder means from said vessel; means operativelyconnecting said piston means to said ladder; and means for maintaining afluid medium under pressure in said cylinder means on one side of saidpiston means as said piston means and cylinder means move longitudinallywith respect to each other to provide an upwardly directed force on saidladder and cutter mechanism to support at least a portion of the weightof said ladder and cutter mechanism and thereby retain the drillingweight of said cutter device against the formation at a selected value;and means for maintaining said fluid medium in said cylinder means at asubstantially constant selected pressure; said supporting meansincluding means for raising and lowering said cylinder means withrespect to said vessel; said supporting means extending above andconnected to the upper portion of said cylinder means.
 13. In dredgingapparatus: a vessel floating in a body of water; a ladder pivotallyconnected to said vessel and extending therefrom; a cutter mechanismcarried by said ladder and including a cutter device for cutting aformation submerged in the body of water; cylinder means; piston meansslidable in said cylinder means; means supporting said cylinder meansfrom said vessel; means operatively connecting said piston means to saidladder; means for maintaining a fluid medium under pressure in saidcylinder means on one side of said piston means as said piston means andcylinder means move laterally with respect to each other to provide anupwardly directed force on said ladder and cutter mechanism to supportat least a portion of the weight of said ladder and cutter mechanism andthereby retain the drilling weight of said cutter device against theformation at a selected value; said supporting means including means forraising and lowering said cylinder means with respect to said vessel;and releasable lock means for securing said cylinder means and pistonmeans to each other whereby raising and lowering of said cylinder meansraises and lowers said ladder and cutter mechanism with respect to saidvessel.
 14. In dredging apparatus as defined in claim 13; said cylindermeans including a guide; said piston means including a piston in saidcylinder means, an upper piston rod portion secured to said piston andextending from said cylinder means, a lower piston rod portion pivotallyconnected to said upper rod portion and slidable in said guide; saidlower rod portion being connected to said ladder; said releasable lockmeans securing said guide to said lower rod portion whereby raising andlowering of said cylinder means raises and lowers said ladder and cuttermechanism.
 15. In dredging apparatus: a vessel floating in a body ofwater; a ladder pivotally connected to said vessel and extendingtherefrom; a cutter mechanism carried by said ladder and including acutter device for cutting a formation submerged in the body of water;cylinder means; piston means slidable in said cylinder means; meanssupporting said cylinder means from said vessel; means operativelyconnecting said piston means to said ladder; means for maintaining afluid medium under pressure in said cylinder means on one side of saidpiston means as said piston means and cylinder means move laterally withrespect to each other to provide an upwardly directed force on saidladder and cutter mechanism to support at least a portion of the weightof said ladder and cutter mechanism and thereby retain the drillingweight of said cutter device against the formation at a selected value;said cylinder means including a guide; said piston means including apiston in said cylinder means; an upper piston rod portion secured tosaid piston and extending from said cylinder means, a lower piston rodportion pivotally connected to said upper rod portion and slidable insaid guide; said lower rod portion being connected to said ladder. 16.In dredging apparatus: a vessel floating in a body of water; a ladderpivotally connected to said vessel and extending therefrom; a cuttermechanism carried by said ladder and including a cutter device forcutting a formation submerged in the body of water; cylinder means;piston means slidable in said cylinder means; means supporting saidcylinder means from said vessel; means operatively connecting saidpiston means to said ladder; means for maintaining a fluid medium underpressure in said cylinder means on one side of said piston means as saidpiston means and cylinder means move laterally with respect to eachother to provide an upwardly directed force on said ladder and cuttermechanism to support at least a portion of the weight of said ladder andcutter mechanism and thereby retain the drilling weight of said cutterdevice against the formation at a selected value; said supporting meansincluding one or more lower sheaves connected to said cylinder means,one or more upper sheaves carried by said vessel, a winch, and cablemeans passing over said upper and lower sheaves and connected to saidwinch to be moved thereby for raising and lowering said cylinder meanswith respect to said vessel; said cylinder means including a guide; saidpiston means including a piston in said cylinder means, an upper pistonrod portion secured to said piston and extending from said cylindermeans, a lower piston rod portion pivotally connected to said upper rodportion and slidable in said ladder; and releasable lock means forsecuring said guide to said lower rod portion whereby raising andlowering of said cylinder means raises and lowers said ladder and cuttermechanism.